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Dive into the research topics where Mayumi Toya is active.

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Featured researches published by Mayumi Toya.


Fertility and Sterility | 2000

Moderate and severe endometriosis is associated with alterations in the cell cycle of granulosa cells in patients undergoing in vitro fertilization and embryo transfer.

Mayumi Toya; Hidekazu Saito; Nobuhiko Ohta; Takakazu Saito; Tomoko Kaneko; Masahiko Hiroi

OBJECTIVE To determine whether folliculogenesis is impaired in patients with endometriosis. DESIGN Prospective study. SETTING Yamagata University School of Medicine, Yamagata, Japan. PATIENT(S) Thirty women participating in an IVF program. INTERVENTION(S) The patients were divided into four groups according to the cause of their infertility: tubal factor (T), n = 7; male factor (M), n = 7; idiopathic (I), n = 7; and endometriosis (E), n = 9. Granulosa cells were obtained from the follicular fluid of each patient and analyzed by flow cytometry. MAIN OUTCOME MEASURE(S) The percentage of granulosa cells in each cell-cycle stage. RESULT(S) The mean (+/- SD) rate of apoptosis in the granulosa cells obtained from the patients with endometriosis was the highest among the four groups (T = 11.7% +/- 3.3%; M = 5.6% +/- 3.8%; I = 9.6% +/- 5.1%; and E = 18.6% +/- 9.6%). The percentage of S-phase granulosa cells was significantly higher in the patients with endometriosis than in all the other patients combined (E = 12.5% +/- 6%; T + M + I = 9.3% +/- 2.9%). The percentage of G2/M-phase granulosa cells was significantly lower in the endometriosis group than in the other three groups combined (E = 2.3% +/- 2.5%; T + M + I = 4.6% +/- 2.1%). CONCLUSION(S) Endometriosis impairs the cell cycle in granulosa cells. This phenomenon may have a detrimental effect on folliculogenesis.


Journal of Assisted Reproduction and Genetics | 2000

Hyaluronic Acid Inhibits Apoptosis in Granulosa Cells via CD44

Tomoko Kaneko; Hidekazu Saito; Mayumi Toya; Takakazu Satio; Kenji Nakahara; Masahiko Hiroi

AbstractPurpose: This study was designed to examine whether hyaluronicacid (HA) inhibits apoptosis in cumulus and muralgranulosa cells and to examine whether this effect of HAwas mediated through CD44. Methods: Mural and cumulus granulosa cells were obtainedfrom in vitro fertilization patients. The cells were culturedwith various concentrations of HA or HA plus variousconcentrations of anti-CD44 antibody without serum supplement.After 24 hr of culture, the cells were fixed and stainedwith Hoechst 33258. One thousand granulosa cells of eachconditions were observed by fluorescence microscopy. Results: HA inhibited apoptosis in both kinds of granulosacells, and anti-CD44 antibody prevented this effect of HA.Conclusions: The incidence of apoptotic granulosa cellswith fragmented condensed nuclei was reduced by HA viaCD44.


Maturitas | 2003

Hormone replacement therapy improves arterial stiffness in normotensive postmenopausal women.

Sayaka Miura; Eiichi Tanaka; Akiko Mori; Mayumi Toya; Kazuhiro Takahashi; Kenji Nakahara; Masahide Ohmichi; Hirohisa Kurachi

OBJECTIVES Aortic stiffness, determined by the pulse wave velocity (PWV), is an independent marker of cardiovascular risk. PWV is mainly influenced by age-associated alterations of arterial wall structure and blood pressure (BP). To determine the impact of hormone replacement therapy (HRT) on arterial compliance in normotensive, postmenopausal women, we examined the effects of HRT on PWV. METHODS Fifty-six postmenopausal women aged 50-70 years were recruited into the present retrospective study from the patients visiting our menopause clinic. Twenty-seven women who were prescribed HRT (14 on estrogen alone and 13 on estrogen plus progestogen) for several months to 6 years and an age-matched group of 29 women not on HRT were studied (Study 1). Nine postmenopausal women were also studied before and at 4 weeks of the treatment of estrogen replacement therapy (ERT) (Study 2). Brachial to ankle PWV (baPWV), which is correlated with aortic PWV, was determined using an automatic device, BP-203PRE. RESULTS In Study 1, PWV was significantly correlated with age in both groups (controls: r=0.392, P=0.035; HRT group: r=0.471, P=0.013), and HRT significantly lowered the PWV value at all ages examined (Mean+/-S.D. of baPWV in controls: 1382.2+/-114.1; HRT: 1245.3+/-124.8, P=0.0001). In Study 2, baPWV decreased significantly after ERT (P<0.05), without a significant change in systolic BP (P=0.851). CONCLUSIONS Estrogen appears to improve arterial compliance independently of BP within 4 weeks.


Fertility and Sterility | 2010

Potential indications for ovarian autotransplantation based on the analysis of 5,571 autopsy findings of females under the age of 40 in Japan.

Koichi Kyono; Masakazu Doshida; Mayumi Toya; Yuri Sato; Jun-ichi Akahira; Hironobu Sasano

Ovarian cryopreservation and autotransplantation could be of potential value for preservation of fertility in the patients with various malignancies. Ovarian tissue should be cryopreserved actively for fertility preservation, but stored tissue should be autotransplanted with much caution until reliable methods are established to detect minimal residual disease in grafts in precise and reproducible manners.


Gynecologic and Obstetric Investigation | 2002

Endometriosis and Oocyte Quality

Hidekazu Saito; Tomofumi Seino; Tomoko Kaneko; Kenji Nakahara; Mayumi Toya; Hirohisa Kurachi

Endometriosis is associated with marked subfertility and various causes for this subfertility have been previously studied. The poor quality of oocytes has been suggested as one possible cause. In this study, we evaluated the quality of oocytes by examining the status of granulosa cells surrounding the oocyte. For this purpose, we analysed the incidence of apoptosis, changes in cell cycle, and oxidative stress in the granulosa cells. Endometriosis patients had a higher apoptotic incidence, more alterations of the cell cycle, and a higher incidence of oxidative stress than patients with any of the other infertility causes (tube, male, and idiopathic factors). These changes might affect oocyte quality, and thus fertility in endometriosis patients.


Journal of Assisted Reproduction and Genetics | 2009

A birth of twins—one boy and one girl—from a single embryo transfer and a possible natural pregnancy

Koichi Kyono; Y. Nakajo; C. Nishinaka; Yasuhisa Araki; Masakazu Doshida; Mayumi Toya; Satoru Kanto

PurposeTo describe a rare case of a birth of dizygotic twins with different-sex infants from a single embryo transfer.Methods and resultsA patient, who had her right ovary and tube removed, and her husband were treated with ICSI and a single embryo transfer. When a single fresh embryo was transferred on day 4, following oocyte retrieval using GnRH agonist-long protocol, two gestational sacs were recognized at 8 weeks of gestation. Healthy twins with a boy and a girl were delivered at 37 weeks 0 days of gestation by a cesarean section. The boy’s weight was 2096g, and his height was 45.0cm, while the girl’s weight was 1988g, and her height was 41.5cm. Peripheral lymphocyte chromosome analysis of the two infants showed normal karyotype, 46, XY (boy) and 46, XX (girl).ConclusionsA single embryo transfer could produce different-sex twins.


Cell and Tissue Research | 2005

Gene expression, cellular localization, and enzymatic activity of diacylglycerol kinase isozymes in rat ovary and placenta

Mayumi Toya; Yasukazu Hozumi; Tsukasa Ito; Morihiko Takeda; Fumio Sakane; Hideo Kanoh; Hidekazu Saito; Masahiko Hiroi; Hirohisa Kurachi; Hisatake Kondo; Kaoru Goto

Female reproductive organs show remarkable cyclic changes in morphology and function in response to a combination of hormones. Evidence has accumulated suggesting that phosphoinositide turnover and the consequent diacylglycerol (DG) protein kinase C (PKC) pathway are intimately involved in these mechanisms. The present study has been performed to investigate the gene expression, cellular localization, and enzymatic activity of the DG kinase (DGK) isozymes that control the DG-PKC pathway. Gene expression for DGKα, -ε, -ζ, and -ι was detected in the ovary and placenta. Intense expression signals for DGKζ and -α were observed in the theca cells and moderate signals in the interstitium and corpora lutea of the ovary. On the other hand, signals for DGKε were seen more intensely in granulosa cells. In the placenta, signals for DGKα and -ι were observed in the junctional zone, whereas those for DGKζ were detected in the labyrinthine zone. At higher magnification, the signals for DGKα were mainly discerned in giant cytotrophoblasts, and those for DGKι were found in small cytotrophoblasts of the junctional zone. DGKζ signals were observed in all cellular components of the labyrinthine zone, including mesenchyme, trabecular trophoblasts, and cytotrophoblasts. DGKε signals were detected in the junctional zone on day 13 and 15 of pregnancy and were diffusely distributed both in the labyrinthine and junctional zones at later stages. The present study reveals distinct patterns of mRNA localization for DGK isozymes in the rat ovary and placenta, suggesting that each isozyme plays a unique role in distinct cell types in these organs.


Reproductive Medicine and Biology | 2017

Efficacy of the endometrial receptivity array for repeated implantation failure in Japan: A retrospective, two-centers study

Tomoko Hashimoto; Masae Koizumi; Masakazu Doshida; Mayumi Toya; Eri Sagara; Nao Oka; Y. Nakajo; Nobuya Aono; Hideki Igarashi; Koichi Kyono

This study aimed to assess the efficacy of the endometrial receptivity array (ERA) as a diagnostic tool and the impact of personalized embryo transfer (pET) for the treatment of patients with recurrent implantation failure (RIF) in Japan.


Journal of Assisted Reproduction and Genetics | 2017

A transportation network for human ovarian tissue is indispensable to success for fertility preservation

Koichi Kyono; T Hashimoto; Mayumi Toya; M Koizumi; C Sasaki; S Shibasaki; N Aono; Yusuke Nakamura; R Obata; N Okuyama; Y Ogura; H Igarashi

PurposeThe purpose of this study was to examine the efficacy of an ovarian tissue transportation network for fertility preservation (FP) for cancer patients in Japan.MethodsPubMed was searched for papers on transportation of human ovarian tissue for FP. We analyzed population, area, number of cancer patients for ovarian tissue cryopreservation (OTC), quality control/assessment and safety, cost of a cryopreservation center for the building for 30 years, and medical fees of cancer patients (operation, cryopreservation, and storage of ovarian tissue).ResultsMore than twenty babies have been born in Denmark and Germany through a transportation system. Up to 400 new patients a year need OTC. The fees for removal, cryopreservation, and storage for 5 years, and transplantation of ovarian tissue are around €5,000, €4,000, and €5,000, respectively. It costs more than €5 million to establish and maintain one cryopreservation center for 30 years. If we have a few cryopreservation centers in Japan, we can cryopreserve 400 patients’ ovarian tissue per year by safer slow freezing and maintain quality control/assessment. We need to lighten the patients’ burden for easy to use FP by a government subsidy and medical insurance coverage.ConclusionsThis model has been termed the Danish model (“the woman stays - the tissue moves”). This is truly patient-centered medicine. We can have maximum effects with the minimum burden. A transportation network like those of Denmark and Germany is the best strategy for FP in Japan. It may be the best system for cancer patients, medical staff, and the Ministry of Health, Labor, and Welfare.


Journal of Assisted Reproduction and Genetics | 2009

Birth of a healthy male infant after transfer of vitrified-warmed blastocysts derived from intracytoplasmic sperm injection with vitrified-warmed oocytes and frozen-thawed spermatozoa

Koichi Kyono; Y. Nakajo; Masakazu Doshida; Mayumi Toya; Yasuhisa Araki

PurposeTo report a successful delivery of a healthy baby after transfer of vitrified-warmed blastocysts derived from introcytoplasmic sperm injection (ICSI) with vitrified-warmed oocytes and frozen-thawed sperm.MethodsA female patient and her husband with non-obstructive azoospermia received a transfer of vitrified-warmed blastocysts from vitrified-warmed oocytes and frozen-thawed sperm. The main outcome measures were fertilization, pregnancy and birth.ResultsNine oocytes were matured and vitrified. When the vitrified oocytes were warmed, six survived with good quality morphology. Using ICSI, frozen-thawed sperm was injected into the six warmed oocytes that survived, and the fertilization rate was 100%. The zygotes were cultured, and five of six early embryos became blastocysts. One of them was transferred, but pregnancy was not achieved. The second time around, two vitrified-warmed blastocysts were transferred resulting in pregnancy, and a healthy boy was delivered.ConclusionsThis is a rare case of a successful birth using a vitrified-warmed blastocyst grown after ICSI with a vitrified-warmed oocyte and frozen-thawed sperm.

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Tomoko Hashimoto

Jikei University School of Medicine

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